feat(milestones): support safe phase-number resets

get-shit-done/workflows/help.md

@@ -192,10 +192,12 @@ Start a new milestone through unified flow.
 - Optional domain research (spawns 4 parallel researcher agents)
 - Requirements definition with scoping
 - Roadmap creation with phase breakdown
+- Optional `--reset-phase-numbers` flag restarts numbering at Phase 1 and archives old phase dirs first for safety
 
 Mirrors `/gsd:new-project` flow for brownfield projects (existing PROJECT.md).
 
 Usage: `/gsd:new-milestone "v2.0 Features"`
+Usage: `/gsd:new-milestone --reset-phase-numbers "v2.0 Features"`
 
 **`/gsd:complete-milestone <version>`**
 Archive completed milestone and prepare for next version.

get-shit-done/workflows/new-milestone.md

@@ -14,6 +14,12 @@ Read all files referenced by the invoking prompt's execution_context before star
 
 ## 1. Load Context
 
+Parse `$ARGUMENTS` before doing anything else:
+- `--reset-phase-numbers` flag → opt into restarting roadmap phase numbering at `1`
+- remaining text → use as milestone name if present
+
+If the flag is absent, keep the current behavior of continuing phase numbering from the previous milestone.
+
 - Read PROJECT.md (existing project, validated requirements, decisions)
 - Read MILESTONES.md (what shipped previously)
 - Read STATE.md (pending todos, blockers)
@@ -82,7 +88,27 @@ INIT=$(node "$HOME/.claude/get-shit-done/bin/gsd-tools.cjs" init new-milestone)
 if [[ "$INIT" == @file:* ]]; then INIT=$(cat "${INIT#@file:}"); fi
 ```
 
-Extract from init JSON: `researcher_model`, `synthesizer_model`, `roadmapper_model`, `commit_docs`, `research_enabled`, `current_milestone`, `project_exists`, `roadmap_exists`.
+Extract from init JSON: `researcher_model`, `synthesizer_model`, `roadmapper_model`, `commit_docs`, `research_enabled`, `current_milestone`, `project_exists`, `roadmap_exists`, `latest_completed_milestone`, `phase_dir_count`, `phase_archive_path`.
+
+## 7.5 Reset-phase safety (only when `--reset-phase-numbers`)
+
+If `--reset-phase-numbers` is active:
+
+1. Set starting phase number to `1` for the upcoming roadmap.
+2. If `phase_dir_count > 0`, archive the old phase directories before roadmapping so new `01-*` / `02-*` directories cannot collide with stale milestone directories.
+
+If `phase_dir_count > 0` and `phase_archive_path` is available:
+
+```bash
+mkdir -p "${phase_archive_path}"
+find .planning/phases -mindepth 1 -maxdepth 1 -type d -exec mv {} "${phase_archive_path}/" \;
+```
+
+Then verify `.planning/phases/` no longer contains old milestone directories before continuing.
+
+If `phase_dir_count > 0` but `phase_archive_path` is missing:
+- Stop and explain that reset numbering is unsafe without a completed milestone archive target.
+- Tell the user to complete/archive the previous milestone first, then rerun `/gsd:new-milestone --reset-phase-numbers`.
 
 ## 8. Research Decision
 
@@ -270,7 +296,9 @@ node "$HOME/.claude/get-shit-done/bin/gsd-tools.cjs" commit "docs: define milest
 ◆ Spawning roadmapper...
 ```
 
-**Starting phase number:** Read MILESTONES.md for last phase number. Continue from there (v1.0 ended at phase 5 → v1.1 starts at phase 6).
+**Starting phase number:**
+- If `--reset-phase-numbers` is active, start at **Phase 1**
+- Otherwise, continue from the previous milestone's last phase number (v1.0 ended at phase 5 → v1.1 starts at phase 6)
 
 ```
 Task(prompt="
@@ -286,7 +314,9 @@ Task(prompt="
 
 <instructions>
 Create roadmap for milestone v[X.Y]:
-1. Start phase numbering from [N]
+1. Respect the selected numbering mode:
+   - `--reset-phase-numbers` → start at Phase 1
+   - default behavior → continue from the previous milestone's last phase number
 2. Derive phases from THIS MILESTONE's requirements only
 3. Map every requirement to exactly one phase
 4. Derive 2-5 success criteria per phase (observable user behaviors)
@@ -378,7 +408,7 @@ Also: `/gsd:plan-phase [N]` — skip discussion, plan directly
 - [ ] gsd-roadmapper spawned with phase numbering context
 - [ ] Roadmap files written immediately (not draft)
 - [ ] User feedback incorporated (if any)
-- [ ] ROADMAP.md phases continue from previous milestone
+- [ ] Phase numbering mode respected (continued or reset)
 - [ ] All commits made (if planning docs committed)
 - [ ] User knows next step: `/gsd:discuss-phase [N]`